The invention relates to a system and a method for interstitial photodynamic and photothermal tumor therapy and diagnosis of a tumor at a tumor site in a body, wherein radiation is conducted to the site for said therapy and diagnosis. The system comprises a distributor of radiation from at least one therapeutic radiation source and a diagnostic radiation source to said tumor, and from the tumor to at least one radiation sensor, respectively.
Within the field of medical therapy of tumor diseases, a plurality of treatment modalities has been developed for the treatment of malignant tumor diseases, e.g. a tumefaction. Operation, cytostatics treatment, treatment with ionising radiation (gamma or particle radiation), isotope therapy, and brachy therapy employing radioactive needles are examples of common treatment modalities. In spite of great progress within therapy, the tumor diseases continue to account for much human suffering, and are responsible for a high percentage of deaths in Western countries. A relatively new treatment modality, photodynamic therapy, commonly abbreviated PDT, provides an interesting complement or alternative in the treatment field. A tumorseeking agent, normally referred to as a sensitizer, is administered to the body intravenously, orally or topically. It accumulates in malignant tumors to a higher extent than in the surrounding healthy tissue. The tumor area is then irradiated with nonthermal red light, normally from a laser, leading to excitation of the sensitizer to a more energetic state. Through energy transfer from the activated sensitizer to the oxygen molecules of the tissue, the oxygen is transferred from its normal triplet state to the excited singlet state. Singlet oxygen is known to be particularly toxic to tissue; cells are eradicated and the tissue goes in necrosis. Because of the localization of the sensitizer to tumor cells a unique selectivity is obtained, where surrounding healthy tissue is spared. The initial clinical experience, using in particular haematoporphyrin derivative (HPD) and delta amino levulinic acid (ALA) are good.
Sensitizers also exhibit a further useful property; to yield a characteristic red fluorescence signal when the substance is excited with violet or ultraviolet radiation. This signal clearly appears in contrast to the autofluorescence of the tissue and can be used to localize tumors and for quantifying the size of the uptake of the sensitizer in the tissue.
The limited penetration in the tissue of the activating red radiation is a big drawback of PDT. The result is that only tumors up to about 5 mm thickness can be treated by surface irradiation. In order to treat thicker and deep-lying tumors, interstitial PDT (IPDT) can be utilized. Here, light-conducting optical fibers are brought into the tumor using, e.g. a syringe needle, in the lumen of which a fiber has been placed.
In order to achieve an efficient treatment, several fibers have been used to ascertain that all tumor cells are subjected to a sufficient dose of light so that the toxic singlet state is obtained. It has been shown to be achievable to perform dose calculations of the absorptive and scattering properties of the tissue. E.g., in the Swedish patent SE 503 408 an IPDT system is described, where six fibers are used for treatment as well as for measurement of the light flux which reaches a given fiber in the penetration through the tissue from the other fibers. In this way an improved calculation of the correct light dose can be achieved for all parts of the tumor.
In the equipment described in SE 503 408 the light from a single laser is divided up in six different parts using a beamsplitter system comprising a large number of components. The light is then focused into each of the six individual treatment fibers. One fiber is used as a transmitter while the other fibers are used as receivers of radiation penetrating the tissue. For light measurement light detectors are swung into the beam path which thus is blocked, and the weak light, which originates from the fibers that collected the light which is administered to the tissue, is measured.
However, such open beam paths result in a strongly lossy beamsplitting and the resulting losses of light drastically impair the light distribution as well as the light measurement. Furthermore, such a system must often be adjusted optically, which is also an important consideration in connection with clinical treatments.